The FAA has rescinded a sweeping notam regarding the reliability of Automatic Dependent Surveillance-Broadcast (ADS-B) surveillance and TCAS after AOPA raised concerns about the ambiguous language, short notice, and month-long duration.
The FAA also has issued new notams that provide greater detail about the affected locations and time frames, shortening the time periods of concern from a month to a matter of hours in some cases. The new notams also provide clearer language regarding the nature of the potential reliability issues and which systems could be affected.
“We appreciate the FAA’s willingness to step back from the original notam, which was causing considerable alarm for pilots, and work with us to provide more accurate and useful data to the aviation community,” said Rune Duke, AOPA director of air traffic and airspace. “We’re optimistic that, since similar activities held over the past decade have not caused problems for civil aviation, there will be no interference. But pilots should still be extra vigilant and report any anomalies with their ADS-B or TCAS systems to air traffic control.”
The original notam issued Sept. 1 announced that, beginning Sept. 2 through Oct. 1, both ADS-B surveillance and TCAS could be unreliable in Virginia, North Carolina, South Carolina, Georgia, and Florida, as well as in airspace extending approximately 200 nautical miles off shore as a result of military exercises in the area.
The wording of the original notam led many general aviation pilots to believe that ADS-B-based traffic information might not be available to them. But a new notam valid on Sept. 5 and 6 made it clear that during the affected hours, ADS-B might be “less sensitive” than usual and that only 1090-MHz ADS-B systems would be affected. No interference is expected for 978-MHz ADS-B systems, which are most commonly used by light GA aircraft. The FAA also issued a notam valid for a few hours on Sept. 9 that provided a specific radius and altitudes of concern, all in areas off the coast of South Carolina.
According to the new notams, the military activity will not generate false TCAS targets and pilots should treat any traffic or resolution advisories as valid.
“This is the kind of solid information pilots need to make informed decisions when they’re planning and conducting flights,” said Duke, who worked closely with the FAA on the new notams.
While the FAA has said it may issue additional notams for related activities between now and the beginning of October, it has not indicated when or where they might be needed.